Thanks for the replies. My Friday afternoon posting skills need a little brushing up
In my ignorance I would not like to cause damage to the engine or gearbox by fitting a prop that has a different design to the one mercury or mariner spec. Its not really the performance that concerns, at the moment.
The 13" and 17" are both alloy, revs are 6000 + for the 13" and around 5000 for the 17".
The Prop is 40mm's clear of the anti-ventilation plate, but the shape and size of the blades plus the weight of the prop are of concern.
I visit Fowey in a few weeks and then I should have the answers on the right pitch.
P.S Anyone got a SS Solas 15"?